Muzzleloading Pressure, Recoil, and Velocity

By Randy Wakeman

For some reason, these three factors are often thought to be directly related, whether the muzzleloading propellant of choice is black powder, Pyrodex, Triple 7, or smokeless powder used as a black powder substitute. They are NOT, and for those interested in such matters, I'll touch on why.

For years, muzzleloading manufacturers have primarily taken the approach of listing maximum powder charges by volumetric grains, either without regard to projectile weight or mumbling a few incomprehensible footnotes about it somewhere in the back of a manual. The Hodgdon Powder Company, like some of their (very) few competitors, does give a maximum charge warning. For example, "100 grains of 50 grain black powder equivalent Triple Se7en pellets" as their maximum allowable charge. On a bottle of Triple Se7en loose powder FFg, you will see, "maximum loads-do not exceed" right beneath 100 grain T7 / 240 grain sabot, 100 grain T7 / 300 grain sabot, and a few other combinations.

Many muzzleloading manufacturers are far worse, giving you nothing to indicate what projectile weights are considered maximum, or even if there IS a maximum projectile weight. It is really past time for the muzzleloading world to grow up a tiny bit.

Most people will readily agree that propellant (gunpowder) produces expanding gas. If that identical type and amount of hot gas is used to push a 200 grain bullet or, alternatively, a 3500 grain cannon ball out of your barrel, it will make a huge difference in pressure. And that difference in projectile weight has everything to do with accuracy, safety, and a "maximum load."

Unfortunately, that is not made readily apparent in the new dark ages of "modern muzzleloading." If you are dumb, you'd better be tough, for muzzleloading manufacturers are not doing their job in describing their recommended loads properly.

In any good reloading manual you are given specific powder charges and bullet weights, with the resulting muzzle velocity and often pressure. Maximum "NEVER EXCEED" powder charges are clearly shown for each bullet weight so that you can be sure to stay below these levels, and be safe. Reloading manuals exist to keep you safe.

If you are a muzzleloader you are a reloader, no two ways about it. Only you control what enters your muzzle before you pull the trigger, and you need reliable information to help you do so properly. So that I can properly offend all the image-conscious muzzleloading manufacturers and all the tender-hearted so-called black powder substitute manufacturers equally, I'm here to tell you that they all royally stink at this. They obviously think you are too dumb to care, and far too dim-witted to comprehend the vital basics of what all competent reloaders have readily understood for decades and decades.

From the Lyman Black Powder Handbook, 2nd Edition, p.p. 171-172: 13,500 PSI, 15,400 PSI, 15,100 PSI, 16,800 PSI, 22,600 PSI, and 23,400 PSI. That is a spread from 13,500 PSI to 23,400 PSI, with one load developing over 73% more pressure than the other. So far, so what? It just looks like a bunch of numbers, and so it is.

However, all these pressures came from the SAME .50 caliber 22 inch 1-24 rate of twist test barrel. All these pressures were developed using the SAME 240 grain Hornady saboted bullet. All these pressures were developed using the SAME 100 grains volumetric measured charge of black powder or a black powder substitute.

Newer, hotter "subs" such as Triple Se7en are not represented, as most were not available when this testing occurred, back in 2001. I would hope that a few eyebrows are raised by now! There is NO SUCH THING as a true black powder substitute. Lyman Ballistic Laboratories is selling no powder, bullets, or projectiles. Their data is without bias; there is no agenda or specific point to prove, which is why their independent test results are referenced here.

One might automatically assume more velocity, more pressure. That assumption would be incorrect. In the above specific case, substitution of two 50 grain Pyrodex pellets produces 20,200 PSI maximum average pressure (MAP) and a muzzle velocity of 1690 fps. As documented by Lyman on these same pages, using 100 grains volumetric of Goex FFFg gives us a small velocity increase, but a dramatic peak pressure DROP to 15,400 PSI MAP. We can burn 120 grains of Goex FFFg, get a muzzle velocity of 1783 fps, and still shoot at a lower pressure of 18,700 PSI.

You will have more free recoil with the faster Goex load than the two pellet load, but less peak pressure. Assuming that more recoil always equals more pressure is also incorrect.

Higher velocity does not necessarily mean more pressure, and recoil does not automatically indicate higher or lower pressure. Not only that, heavier projectile weight does not automatically mean higher pressure, either. On p. 173 of the same Lyman manual, a 300 grain Hornady bullet/sabot pushed by 100 grains of Elephant FFg produces only 14,300 PSI. That same Elephant FFg produces more pressure with the lighter 240 grain Hornady XTP/sabot. Same way with the two pellet load: the tested pressure drops with the use of a 300 grain Hornady sabot compared to a 240 grain Hornady sabot.

The peak pressures cited are hardly the lowest pressures recorded in this barrel by black powder and black powder substitutes: 27,000 PSI, 29,000 PSI, and even 30,200 and 33,500 PSI peak pressures are published. No loose powder charge heavier than 120 grains was tested, so this is hardly any "limit."

If this reads like a confusing mess, you are reading correctly--that's exactly what it is. We have not even started to look at the differences caused by specific manufacturer's barrel tolerances, different rates of twist, shot start pressure, and rifling depth. Nor are the effects of temperature and barrel fouling condition addressed, and all sabot formulations are clearly not alike. Nor do different conical bullet styles and lead alloys produce the same results, though they may weigh the same.

I grow weary of the uneducated bile spouted by some in the industry that warn of the "higher pressures" of smokeless powder. That may be true, but it equally may NOT be true.

Consider that the maximum service pressures allowed by SAAMI for 28 gauge, 20 gauge, 16 gauge, and 12 gauge (2-3/4 in. and 3 in. shotshells) do not exceed 12,500 PSI in any case, yet all are smokeless powered. Every single black powder and black powder substitute load cited above smashes the rules of what you can use in your modern smokeless powder shotguns and deer-hunting slug guns. If all of this verifiable, independently documented information makes you wonder just a bit, then this article has served its purpose. I certainly do.

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Copyright 2005 by Randy Wakeman. All rights reserved.